The Bohr-Heisenberg Meeting from a Distance

When Werner Heisenberg visited his old mentor Niels Bohr in Nazioccupied Copenhagen in the dark days of the Second World War, little could the pair have foreseen that their meeting would arouse so much interest among future historians of science. The study of their meeting is now something of a cottage industry.

Mara Beller

Ig. Tamm

Jan Faye, Stefano Furlan, Rasmus Jaksland

John Wheeler tells us that Niels Bohr and Werner Heisenberg met with the Danish philosopher Harald Høffding in the summer of 1927 to discuss the philosophy of quantum mechanics—following the disagreement between Bohr and Heisenberg about the uncertainty relations and right before Bohr’s introduction of his complementarity interpretation of quantum mechanics in Como, Italy, in September 1927. Is this evidence that Høffding had an even greater influence on the early development and interpretation of quantum mechanics than hitherto believed? We trace the historical sources of the story, which Wheeler first heard from Casimir, who apparently was present when the episode took place. We argue that the episode cannot have taken place earlier than 1929 and propose an event in November 1929 as its likely origin. What remains true is that Bohr, Casimir, and Høffding did meet, but the meeting is less remarkable than in Wheeler’s retelling. Nonetheless, Casimir’s role in the story adds new evidence for Høffding’s influence on Bohr. Heisenberg presence, though, is entirely of Wheeler’s invention. We use this rendering to illustrate how Wheeler operated as a storyteller of quantum mechanics from the 1980s to his death.

Abner Shimony

John Bernard Gallagher

During the week of September 15, 1941, Niels Bohr and Wemer Heisenberg met secretly in Copenhagen, Denmark. These Nobel physicists worked together in the 1920s to construct a new quantum physics. The Copenhagen Interpretation consisted of statistical quantum mechanics, the Uncertainty Principle, and Complimentarity, which revolutionized perceptions of atomic phenomena and challenged the scientific community with their conceptions of classical Newtonian causality. At the time of the meeting, Germany occupied Denmark and Heisenberg led the German effort to develop practical applications of nuclear fission. Bohr’s and Heisenberg’s meeting ended with anger and frustration leading to the separation, personally and professionally, of these two men. Owing to a lack of documentation and the varying opinions over the events of 1941, I propose to use the scientific principle of uncertainty, developed by Heisenberg in 1927, as a metaphor to broaden our understanding of the meeting between these men. Instead of using the two pairs of conjugate variables, as defined by the Uncertainty Principle, I will use four-square variables that allows for an alternate interpretation of the 1941 Bohr-Heisenberg meeting. The four-square variables involve aspects of Werner Heisenberg’s life. These are the development of his scientific work, the formation of the scientific community through collaboration, the social, cultural, and political context of Germany, and the personal and professional relationship between other physicists and between Bohr and Heisenberg themselves. My thesis seeks to determine what was said between these men that led to the disruption to their relationship. My conclusions limit the indeterminacy of the event and brings a level of acceptable uncertainties that illustrate above all that Heisenberg was a man of Germany.